Fig. 4.

Suppression of SNAP-induced cGMP levels via iNOS. Longitudinal muscle cells isolated from colons of control and TNBS-treated mice (A) or from muscle strips cultured in the presence of IL-1β (10 ng/ml) (B) or TNF-α (1 nM) (C) for 48 hours were treated with different concentrations of SNAP. In some experiments, muscle strips were cultured with IL-1β (10 ng/ml) or TNF-α (1 nM) in the presence of iNOS inhibitor 1400W (10 µM) for 48 hours. cGMP levels were measured in the presence of 100 µM IBMX as described in Materials and Methods. Basal cGMP levels were not significantly different between control and TNBS-treated mice (0.24 ± 0.05 versus 0.21 ± 0.04 pmol/mg protein) or between control and cytokine-treated muscle strips (0.22 ± 0.04 versus 0.26 ± 0.05 pmol/mg protein). Values are the means ± S.E.M. of five experiments. **P < 0.01, significant inhibition in SNAP-induced cGMP formation.